Method of making insulated electrical conductors



1 June 16, 1942. 4 v. I... JOHANNESSEN 2,286,807

METHOD OF MAKING INSULATED ELECTRICAL CONDUCTORS Filed Sept. 15, 1938FIG. 2

.ME7I4L FELTED SHEATH OF CONDUCTOR STRAND WA TE R PROOFED FIBRES '/N VEN 7' OR By V. L JOHANNESSEN A TIORNEV Patented June 16, 1942 METHOD OFMAKING INSULATED ELECTRICAL CONDUC'IORS Vaughn L. Johannessen, Cranford,N. J., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New york Application September 15, 1938, Serial No.230,030

3 Claims.

" to include in the paper pulp sheath some additional material to renderthe fibers of the sheath more adherent together and substantiallynonabsorptive of water, whether in the form of atmospheric containedvapor or as liquid.

Objects of the invention are to provide a method of making an electricalconductor having an insulatin sheath comprising matted fibers and amaterial to render the fibers .of the pulp water repellant and also toincrease the insulating quality of the sheath.

With the above and other objects in view the invention may be embodiedin a method of proaxis horizontal in such fashion that its lower ducingsuch a paper insulated conductor which is characterized by a step ofbeating a suitable proportion of the water repellant material into thewet paper pulp before the pulp is used to form the sheath on the wire,whereby a certain amount of the water repellant-material is caused to.adhere in powder form to the outer surface of 'each fiber before thelatter are felted together;

and the method is further characterized by including a final step inwhich after the wet pulp has been formed into a sheath about the wirethe wet sheathed wire is suitably heated not only to drive off waterfrom the sheath but also to melt the powdered water repellant materialadherent to the fibers to form a coating on the individual fibers in thefelted mass.

Other objects and features of the invention will appear from thefollowing detailed description of an apparatus constructed to carry outthe method of the invention taken in connection with the accompanyingdrawing in which the same reference numerals are applied to identicalparts in the several figures, and in which- Fig. 1 is a diagrammaticview of an apparatus constructed for carrying out the method of theinvention; and

Fi 2 is an enlarged fragmentary view of a portion of a strand producedby the apparatus and method of Fig. 1.

The apparatus herein disclosed comprises a supply reel 3| to contain asupply of wire which is to be provided with a suitable sheath 29 portiondips below the level 22 of the pulp mixture in the tank. The strand 30passing down into the tank makes contact with the drum 2| at a point 33some distance below the level 22 and passes on around the drum to aboutthe top point of the drum. ;Here it makes contact with and accompaniesan endless belt 35 of felt running over guide rollers 38 and 36 and overa belt driving roller 31 which itself is driven by a, motor It.

The drum 2| is a hollow shell suitably supported by means (not shown) onshaft 25 and the shell is foraminous. A pump (not shown) whose intake isindicated at 24 keeps the level of the pulp suspension within the drumat a line 23 below the level 22 outside of the drum and still above thepoint 33. Hence the suspension outside of the druin tends to be drawnthrough the drum between levels 22 and 23, thus forming on the left handside a thin mat of felted fibers on the drum. Then the wire 30 is laidon the drum over this felt and continues along with the drum until itagain rises above the level 23 on the right, when further pulp materialis laid on the drum overv the wire 30. Thus, as the wire emerges fromthe suspension but still on the drum at the right hand side of thelatter it is enclosed within a ribbon of felted pulp and when the wireleaves the drum 2| at the top of the latter and passes against the feltbelt 35 it is accompanied by this ribbon like sheath of felted paperfibers. The wire and its crude sheath leave the belt 35 at the top ofthe belt driving roller 31 and pass together into a sheath formingdevice 39 in which the flat ribbon of crude fiber is formed and polishedinto a substantial cylindrical sheath about the wire.

From the polisher 39 the wir with its still wet sheath passes through aheating device 40 in which the water is removed from the sheath andthence to a take-up reel 4 l The procedure and apparatus thus fardescribed is not new but is described and fully disclosed in applicationSerial No. 110,611, filed November 13, 1936 by John N. Selvig, uponwhich application Patent No. 2,180,554 was granted on November 21, 1939,and hence it is thought that it is not necessary to describe thesegeneral features of the process and apparatus more in detail at thistime since reference may be had to the above application for suchdetail. 7

The pulp suspension supplied to the tank 20 is ordinary unsized paperpulp such as is used for the manufacture of good quality newsprint paperand the like in the paper making art, and being familiar and well knownrequires no further description here except to say that it consistssubstantially entirely of fairly pure cel lulose fibers derived fromwood, and beaten up in water so that the suspension comprises about 6parts by weight of wood fiber in about 194 parts by weight of water. Asone step in the method of the present invention, however, when the crudewood fiber as received from the paper pulp manufacturer is torn apartand beaten up in water to make this pulp there is added about 3 parts byweight of a water repellant material, making the water proportion thenabout 191 parts by weight. This material is preferably a powderedcondensation product of the oil which is found in the shell of thecashew nut. The characteristics of this oil and the manner of preparingsuitable condensation products therefrom are described in detail in U.S. Patent 1,725,791 issued August 27, 1929, to Mortimer T. Harvey, andhence will not be further described here except to say that theparticular condensation product here in question is one which meltsbetween 180 F. and 200 F., and as found in commerce is fairly dense,fine grained powder apparently totally insoluble in and unaffected bywater. This powdered material is beaten in an ordinary pulp beater withthe pulp until it is thoroughly and uniformly disseminated throughoutthe liquor and then the liquor is transferred to the tank 20. It isbelieved that at this time substantially all of the cellulose fibers inthe suspension are more or less uniformly coated with more or lessscattered particles of the powder.

In the method of the invention this suspension having the waterrepellant material in powder form beaten into it is used in the tank 20in the manner described above, instead of the ordinary pulp suspensioncustomarily used. Thus, when the strand with its formed but still wetsheath passes from the polisher 39 into the drying oven 40, each of thematted fibers which compose the felt like sheath on the wire isindividually more or less coated with powdered water repellant material.

While an ordinary, externally heated drying oven 40,,such as isdescribed in the copending application of John N. Selvig aboveidentified, is satisfactory, nevertheless it is preferred to substitutefor the ordinary oven 40 an induction heating coil through the axis ofwhich the sheathed wire passes from the polisher 39 and over the guidesheave 21 to the take-up reel 4!. The coil is supplied with highfrequency electric current of such voltage and frequency as will providea strong alternating electromagnetic field within the coil within whichthe crude sheathed strand passes. In the well known manner of inductionheating, eddy currents are generated within the wire which are convertedin the body of the wire into heat. By suitably regulating the currentsupply to the induction coil the wire may be thus heated to the point atwhich first the water contained in the crude pulp sheath is driven offand, secondly, the finely powdered cashew oil product on the individualfibers is caused to melt and become a thin substantially waterproofcoating upon each fiber individually. Thus, when the finished product iswound up upon the take-up reel ll it is a wire having a seamless sheathof individually water repellant felted fibers of the cellulose.

The sheath thus coated is physically and mechanically a very differentthing from that obtained by applying a waterproofing material, such as aresin dissolved in a volatile solvent, to the finished sheath andsubsequently driving off the solvent, for in such case the solventcarries the resinous waterproofing material into the substance of thefiber and a much larger ratio of resin to fiber is required to producethe same degree of water repellence as is obtained in the presentmethod, in which the waterproofing material is applied substantiallyonly to the surface of each fiber and does not enter materially into thebody of the fiber.

It has been found that a generally satisfactory product can be made bythe use of an externally heated oven 40, although in some instances itis found that superficial fibers of the sheath may become dried out andadhere together in a substantially impervious film before the body ofthe film is thoroughly dry and thus prevent the escape of the residualmoisture under the film.

For this reason it is thought preferable to use induction heating in themanner described to dry the wet sheath, because by so doing the sheathis heated from within outwardly, and the escape of the vaporizedmoisture from the body of the sheath is neither prevented nor hindered,thus insuring a substantially moistureless product.

The new type of coated strand produced by the use of the method andapparatus disclosed is not claimed herein, being disclosed and claimedin copending application Serial No. 288,475, a division of the presentapplication, filed August 5, 1939, by the present inventor and uponwhich application U. S. Patent No. 2,249,955 was granted to the presentinventor on July 22, 1941. While a particular illustrative embodiment ofthe invention has been herein disclosed the invention is not limited tothe specific details of the disclosure but may be modified and departedfrom in many ways without departing from the spirit and scope of theinvention as pointed out in and limited solely by the appended claims.

What is claimed is:

1. A method of making an insulated electrical conductor which methodcomprises steps of mixing together about 6 parts by weight of paper pulpand about 3 parts by weight of a powdered solid condensation product ofcashew nut oil having a melting point from F. to 200 F. by beating thesame together in about 191 parts by weight of water to disperse the pulpfibers in the water and to coat each fiber with grains of the powderedproduct, forming from the resulting pulp suspension a ribbon of pulpcombined with a conductive strand, forming the ribbon into asubstantially cylindrical sheath about the strand, and so heating thesheathed strand as to drive off moisture from the pulp and to melt thegrains of powder on each of the felted fibers into a coatingsubstantially superficially covering but not impregnating each fiberindividually.

2. A method of making an insulated electrical conductor which methodcomprises steps of mixing together about 6 parts by weight of paper pulpand about 3 parts by weight of a powdered solid condensation product ofcashew nut oil having a melting point from 180 F. to 200 F. by beatingthe same together in about 191 parts by weight of water to disperse thepulp fibers in the water and to coat each fiber with grains of thepowdered product, forming from the resulting pulp suspension a ribbon ofpulp combined with a conductive strand, forming the ribbon into asubstantially cylindrical sheath about the strand, and passing thesheathed strand through an energized induction coil to so heat thesheathed strand from within outwardly as to first drive off moisturefrom the pulp and then to melt the grains of powder on each of thefelted fibers into a coating substantially superficially covering butnot impregnating each fiber individually.

3. A method of making an insulated electrical conductor which methodcomprises steps of mixing together about 6 parts by weight of paper pulpand about 3 parts by weight of a powdered solid condensation product ofcashew nut oil having a melting point from 180 F. to 200 F. by beatingthe same together in about 191 parts by weight of water to disperse thepulp'fibers in the water and to coat each fiber with grains of thepowdered product, forming from the resulting pulp suspension asubstantially cylindrical sheath about the strand, and so heating thesheathed strand as to drive off moisture from the pulp and to melt thegrains of powder on each of the felted fibers into a coatingsubstantially superficially covering but not impregnating each fiberindividually.

VAUGHN L. JOHANNESSEN.

